Esters of cyclohexadiene polycarboxylic acids



Patented June 13, 1950 ESTERS OF CYCLOHEXADIENE POLYCARBOXYLIC ACIDSPaul C. Condit, Berkeley, Calif., assignor to Cali- I fornia ResearchCorporation, San Francisco, Calii., a corporation of Delaware NoDrawing. Application February 8, 1946. Serial No. 646,496

3 Claims.

This invention relates to new and useful compositions of matter andmethods of preparing the same.

More particularly, the invention is concerned with polymeric materials,monomers therefor, and especially with the production of polymericesters of cyclohexadiene polycarboxylic acids.

It has been discovered that polymeric esters of cyclohexadienepolycarboxylic acids possess valuable and apparently unique properties.These properties render the polymeric esters particularly useful inplastics, coating compositions, adhesives and the like.

It has been found, for example, that esters of cyclohexadienedicarboxylic acids may be polymerized and that those polymeric esterswhich are essentially linear in nature have the property of air dryingby oxidation and/or polymerization in a manner analogous to that of thenatural drying or semidrying oils, even though these synthetic esterscontain no drying oil constituent.

Further, it has been discovered that esters may be obtained inaccordance with this invention which are capable of conversion tovaluable infusible or ditficultly fusible solids by thermosetting actionwithout the necessity of eliminating water, an alcohol, etc., as in acondensation poly- (Full formula) (Formula abbreviated for convenience)Thus, the position of the carboxyl groups in the above compoundis (1),(2).

In the terminology here used, the sign A signifies a double bond and A1would indicate a double bond between the (1) and (2) carbon atoms of thering; A2 would place the double bond between the (2) and (3) carbonatom, etc. The complete name of the above acid would, therefore, beA3,5-cyclohexadiene dicarboxylic acid-1,2. When the stereo-isomer ofthis acid is the cis form it is anhydride forming; if the trans type, itdoes not form its own anhydride but rather the anhydride of the cis acidwhen treated with suitable reagents such as acetic anhydride.

The foregoing and other acids of this series are sometimes termed.dihydrophthalic acids, and identifying numbers utilized merely to placethe position of the added hydrogen atoms; for example, the foregoingacid could be designated 1,2- dihydrophthalic acid. But this terminologyis misleading insofar as it implies equivalency between phthalic acidsand the cyclohexadiene dicarboxylic acids. Accordingly, thisspecification utilizes terminology which is believed to describe moreaccurately the nature of the compounds and compositions discovered.

The compounds and compositions of this invention may be derived from anyone or more of the following exemplary cyclohexadiene dicarboxylicacids:

ii -o H C 0 OH C O 0 H l O c o H Trans-A3,5- Cis-A3,5-A2,6-cyclohexadiene cyclohexadiene dicyclohexadiene didicarboxylicacid-1,2 carboxyllc acid-1,2

oarboxylic acid-1,2

AlA'cyciohexadiene dicarboxylic acid-1,4

Of the cyclohexadiene dicarboxylic acids, the comugated diene acids arepreferred, and derivatives of the A3,5 or A2,6-cyclohexadienedicardesirable. A mixture predominantly trans-A3,!- cyclohexadienedicarboxylic acid-1,2 but containing small amounts ofA2,6-cyclohexadiene dicarboxylic acid-1,2 has been found effective forthe purpose of this invention.

In accordance with the invention, a monomer may be formed byesteriflcation of a suitable cyclosome glycerolto yield controlledcross-linking in final polymerization stages is particularly useful. Athird type of polymeric ester of cyclohexadiene polycarboxylic acids maybe obtained by p lymerization of the monohydric alcohol esters, e. g.,methyl or ethyl esters.

Polymerization of the foregoing monomeric esters may be controlled toyield an initial polymer which is essentially linear in nature and has aviscous liquid to thermoplastic solid consistency. This initial polymermay be further treated to form an intermediate stage resinous 4 productwhich is semicross-linked; i. e., crosslinked to a minor but suflicientextent to render the composition diiilcultly, if at all, soluble incommon solvents and yet plastic or moldable. 5 The intermediate stagepolymer is, in turn, convertible to a substantially insoluble, infusiblepolymeric or resinous product.

Each of the three type polymers above described, i. e., the linearpolymer, the semicrosshexadiene olycarboxylic acid with a polyhydric lolinked polymer, and the final three-dimensional alcohol. A preferredmonomer is of the type'forinfusible polymer, has a field of greatestutility. mula For example, the linear polymers are useful in coating orimpregnating compositions and are E capable of air drying by oxidationand/or polymerization in a manner analogous to that of the naturaldrying oils. The intermediate stage or semicross-linked polymer isespecially useful in molding or other compositions when plasticity is ordesired, and the third stage product is of value in protective coatingsor in molded articles and the like, by reason of its relative inertnessand resista ance to solvents.

The type formula for a typical linear polymer derived from acyclohexadiene dicarboxylic acid and a polyhydric alcohol is as follows:

0 where X and Y are polyhydric alcohol residues E which may or may notcontain additional hy- U droxyl groups. Such monomers are frequentlydifficult to isolate because of their tendency to polymerize. Adesirable resin-forming composi- 8 tion of this invention is, therefore,a solution of a In the above formula X represents a polyhydriccyclohexadiene rpoxylic acid in a p alcohol residue and the structure inbrackets is dric alcohol with or without additional solvent. repeated ntimes to form a long chainnke struc The may contain one or more ture. Inthe above formula, nmaybedesignated the above mommelic esters togetherwith degree of polymerization and may vary from mers thereofabout 2 toabout 5 or more in the preferred com- Exa ples of polyhydric alcoholsWhwh may be positions of the linear type. Lower degrees of reacted withcyclohexadiene dicarboxylic acids to polymerization give less viscousliquids, and obtain resinous or polyme a compositions are 40 tivelyhigher degrees of polymerization yield glycol, glycerol; polye hyle eglycols- Such 85 highly viscous or even hard solid polymeric maethyleneglycol, trlethylene glycol, tetmethylene terials. This type formularepresents essentially glycol; pentaerythri bl and manmtolthe type ofcomposition formed in the foregoing Alkene oxides, such as ethyleneoxide, propylene fi st stage of polymerization. oxide, and butyleneoxides, may be substituted A very vamable property of t above nnear forpolyhydric alcohols in the ester-forming retype polymer is t fact t t tmay be converted action. Glycol a glycerol are Presently to across-linked, three-dimensional type of polyferred polyhydroxy alcoholswhich illustrate two mer without the necessity of splitting out water,different types of polymeric compositions emalcohol or the like, orwithout requiring the presbraced by this invention. Mixtures of the poyence of drying oil constituents. Cross-linking of hydric alcoholslikewise may be utilized to obtain the linear type polymer may occur bysimple admixed esters; for example, a mixture consisting ditionpolymerizationto connect two linear chains predominantly of a glycol butalso containing substantially as indicated below:

o-o c-o-x-o-o the above addition type cross-linking still occurs,

but oxygen may be included in the connecting linkage. The exact natureof the cross-linkage on air drying or oxidation is not known, but is- 60t cross-linkage may, but certainly need not necessarily occur. Forexample, if an essentially linear polymer of the above described time bemixed with a dicarboxylic acid anhydride of the type H o i-o-i z-o-iross-linkage and thermosetting effected in the absence of air densation,or other oxidizing agents, a polymer of the followtic formula:

H o C-Oli-O-C Q 5 thought to be similar to that effected in the drying"of linseed oil and the like.

This is true because of the residual free hydroxyl groups which arepresent in fi-ox-o-c This type of polymer is capable of c by oxidation,and by con 0 -oxo--- The esteriiication of cyclohex'adlene dicarboxylicacids with glycerol, or other polyhydroxy a1- cohols containing morethan two hydroxyl groups 5 f rm l to form an essentially linear polymer,increases the number of points in the chain at which crosslinking mayoccur.

the linear chain. These linear polymers are usum ally syrupy liquids tothermoplastic solids and contain the following typical chain elements:

' o J-o-ag-o by addition, as is illustrated by the diagramma where thedotted lines indicate illustrative potening type may be obtained by acondensation type tial points of cross-linkage. All of the above typescross-linkage:

-o-x-o- -o-c c-ox-o-o c-oit-o-o Q i Q i o -o-o co-h-oi i-O-lg-O- Anothertype of polymer utilizing the glyceride type polyester of cyclohexadienedicarboxylic acid is obtained by reaction of the free hydroxyl groups ina linear polymer with such reagents as an unsaturated acid, anhydride,or nitrile, such as acrylic acid, maleic anhydride, or acrylonitrile;or, if desired, with aliphatic monocarboxylic acids such as long chainoil solubilizing fatty acids. Examples of such long chain acids arelauric, myristic, stearic, arachidic, oleic, and the like acids.Polymeric esters of the multiple or mixed type will be described in moredetail hereinafter.

The following specific examples will serve to 11- lustrate thederivation and preparation of the esters of this invention and to guidethose skilled in the art in obtaining the same.

Example 1.--A linear polymeric ester comprising the reaction product ofA3,5-cyclohexadiene trans-dicarboxylic acid-1,2 (which may contain asmall amount of a A2,6 isomer when desired) and ethylene glycol wasprepared by mixing 10 g. of this acid with 4 cc. (7/6 of theory) ofethylene glycol and heating in an oil bath maintained at about 175 C.The reaction mixture was protected from oxidation by bubbling carbondioxide therethrough and heating was continued for 1% hours. Theoriginal suspension turned to a clear solution as it reached bathtemperature and gradually became more and more viscous as heatingproceeded. The product after 1% hours was a clear, light yellow, veryviscous oil and was tacky to the touch. A chloroform solution of theproduct decolorized a carbon tetrachloride solution of bromineinstantaneously and exothermally. This viscous oil is a polymeric esterwhich is actively unsaturated and capable of addition polymerization toform either a semicross-linked difllcultly soluble polymeric ester onexposure to air or a substantially insoluble three-dimensionalcrosslinked polymer on heating. These last features, together withutility in coating compositions, are illustrated in Examples 2, 3 and 4.

Example 2.--A coating composition was prepared by dissolving 2.5 g. ofthe polymerized viscous reaction product of Example 1 in 5 cc. ofchloroform as a solvent. This solution was painted in a thin film on aclean glass plate, ex-

posed to sunlight, and allowed to dry. After 6 weeks the resin filmwas'a semicross-linked polymeric ester as shown by the fact that it wasnormally solid and partially insoluble in chloroform, whereas theoriginal linear polymer of Example 1 was a viscous liquid completelysoluble in chloroform. The cross-linking was effected by additionpolymerization in the presence of oxygen and at normal room temperature.Condensation polymerization is precluded under these conditions sincethe reaction condition are not such as would produce esterification andthe elimination of water or ethylene glycol.

The polymeric esters of this invention are responsive to the action ofmetal salt oxidation catalyst, commonly designated "driers in the paintand varnish industry. This valuable property is illustrated in thefollowing example.

Example 3.-2.5 g. of the polymerized viscous reaction product of Example1 was dissolved in 5 cc. of chloroform, and 0.33 cc. of a commercialmetal naphthenate drier containing 17% lead and 1.7% cobalt was added tothis solution. The coating composition so prepared was painted in a thinfilm on a clean glass plate, and exposed to sunlight, and allowed to dryunder the same conditions as in Example 2, above. This film polymerizedby addition and/or oxidation much more rapidly than that of Example 2.It had is lost most of its tackiness after 24 hours and was nearlycompletely dry to the touch after 48 hours. The polymer thus obtainedwas a semicrosslinked resin, normally solid, and partially insoluble inchloroform.

The linear polymer of Example 1 is thermosetting and capable ofconversion to a threedimensional, insoluble, relatively hard resin.

Example 4.A coating composition was prepared as in Example 2, and thesolution painted on a clean glass plate. The resin film thus obtainedwas heated at a temperature of from about to about C. in an electricallyheated oven. At the end-of 4 hours of heating the plate was removed fromthe oven and cooled. Examination revealed that the resin was a hard,thermosetting, cross-linked polymer completely insoluble in chloroformand substantially untouched by the action of this solvent at roomtemperature. The coated plate was inspected over an extended period andno spalling, cracking or further discoloration of the film occurred.When scratched with a knife, the film proved to be as hard as it wasoriginally after baking, and a fragment chipped off was flexible andshowed no apparent embrittlement.

By way of comparison, it is noted that the foregoing linear polymers ofExample 1 dry at room temperature in air somewhat faster than rawlinseed oil. The resin film left by the dried coating composition iscomparable to, but not as hard as, the one formed under the sameconditions by linseed oil. The baked resin films are quite hard butnonbrittle, as above noted.

Example 5.A polymer was produced using A3,5-cyclohexadienetrans-dicarboxylic acid-1,2 with glycol and the resinification carriedto the gelation stage in this example. The batch formula was:

10 g. A3,5-cyclohexadiene trans-dicarboxylic acid- 1,2 4 cc. ethyleneglycol The ingredients were mixed and heated in an oil bath at aboutl60-to C. Carbon dioxide was bubbled through the reaction mixture and,to follow the course of the reaction, samples were removed periodically,dissolved in alcohol, and titrated with alcoholic KOH.

Neutralization Time, hours 0.

(mg. KOH/g.)

10 g. A3,5-cyclohexadiene trans-dicarboxylic acid- 100 cc. ethyleneglycol The batch was refluxed at the boiling point of the reactionmixture under substantially atmospheric pressure using a steam jacketedreflux condenser to prevent loss and condense the boil- N eutmlizationTime, hours No. (in KOH] 00. so ution) 5 cc. of liquid were obtainedoverhead in the 7.5 hours. 60 cc. of the ethylene glycol were thenremoved by vacuum distillation under 2 mm. of mercury pressure. Theresulting concentrated solution was a viscous liquid ester completelysoluble in water. 1 cc. required 10.4 mg. of KOH. The completesolubility in water of the monomeric ethylene glycol diesterdistinguishes it from the polymeric ester. The solution contained asmall amount of the monomeric monoester of ethylene glycol as indicatedby the fact that 1 cc. required 10.4 mg. of KOH for neutralization. Byway of comparison, it should be noted that the original solution(without any esteriflcation) would require approximately 67 mg. of KOHto neutralize 1 cc., and the concentrated solution (after removal of theethylene glycol by vacuum distillation) would require 167 mg. of KOH percc. The acid ester, that is, the

monomeric monoester of ethylene glycol, would require 33.5 mg. of KOHper cc. of the original solution and 83.5 mg. of KOH per cc. of theconcentrated solution formed by vacuum distillation. The fact that theester was completely soluble in water shows that the amount of polymericester present was negligible since these polymers have been found to bewater-insoluble.

Either the monomeric ester or the solution thereof is capable of furtherpolymerization on heating to form polymeric esters of the type hereindescribed.

Example 7.-A soluble, plastic, solid polyester of A2,6-cyclohexadienedicarboxylic acid-1,2 from A3,5-cyclohexadiene dicarboxylic acid-1,2 wasprepared as follows: A3,5-cyclohexadiene transdicarboxylic acid-1,2 wasmixed with a 5.1% molar excess of ethylene lycol. The mixture wasimmersed in a bath at 120 C. and heated at 120 to 147 C. for 1 hour and58 minutes. After standing over night at room temperature, the partiallyreacted mixture was immersed in a bath at 32 C. and the temperatureraised to a maximum of 151 C. during a period of 2 hours and 6 minutes.The temperature was then raised from 151 to 174 C. over a period ofminutes and the temperature maintained at 171 to 177 C. for 37 minutes.At this stage the reaction mixture was removed from the bath for about 1hour and heating resumed at 170 to 176 C. for 48 minutes. During anadditional and final 45 minutes of heating the temperature wasmaintained in the range of 166 to 176 C. and the pressure at 3 mm. toefiect further polymerization and to remove unused glycol together withany water present. During this period a small amount of white soliddistilled from the reaction mixture. The system was separated from theatmosphere with a carbon dioxide trap during the reaction period and astream of CO2 gas was drawn through the reaction mixture as it washeated under vacuum. The product remaining in the reaction flask was athick, yellow syrup that solidified .on cooling to a clear, yellow,glassy solid. A 95.5% yield of this resin was obtained calculated on thebasis of complete reaction of one mol of acid per mol oi. glycol. Thepolymer was found to be soluble in acetone and 5% aqueous sodiumbicarbonate, almost completely soluble in chloroform, partly soluble inhot ethyl alcohol, and insoluble in water, benzene, carbontetrachloride, petroleum ether and diethyl ether. The product flowed at66.6 to 70.6 C. in a copper block melting point apparatus.

It is to be noted that in the preparation of this polymer. the totalperiod of heating was about 6% hours of which 2% hours was at about C.Determination of the ultraviolet light absorption characteristics ofthis polymer revealed that the A3,5-cycl0hexadiene dicarboxylic acid-1,2had isomerized by reason of the prolonged high temperatures to which ithad been subjected during preparation, and that the polymeric ester wasessentially an ester of the A2,6- cyclohexadiene dicarboxylic acid-1,2.

The following analyses were obtained on this reaction product:

This corresponds to a polyester with an average composition of aboutfive cyclohexadiene dicarboxylic acid groups joined through fourethylene glycol groups.

Example 8.The preparation of a polymeric cyclohexadiene dicarboxylicacid ester of a polyhydroxy alcohol containing more than 2 hydroxylgroups is illustrated by the reaction of A3,5-cyclohexadienetrans-dicarboxylic acid-1,2 with glycerol to obtain an insoluble solidthree-dimensional polymer:

A3,5-cyclohexadiene trans-dicarboxylic acid- 1,2 and glycerol were mixedin chemically equivalent quantities (3 mols of acid to 2 mols ofglycerol) and heated at l86.5 to 194 C. for 1 hour and 43 minutes whilecarbon dioxide was passed through the reaction mixture. The temperatureof heating was then raised to 193 to 195 C. and maintained for 45minutes under a pressure of 10 min. of mercury. A small amount of whitesolid distilled along with the water formed during the reaction.Gelation of the reaction mixture had occurred at the end of 65 minutesof reaction and the final product was a clear yellow, hard, glassysolid, insoluble in water, 5% aqueous sodium bicarbonate solution,acetone, mesityl oxide, ethyl alcohol, butyl acetate, ethyl ether,carbon tetrachloride, chloroform, ethylene chloride, toluene, petroleumether, and petroleum thinner. The product swelled slightly in dioxaneand Cellosolve. On the basis of complete reaction the yield was 94.6% ofthe theoretical. Analysis showed this material tocontain 59.02% carbonand 5.19% hydrogen. The saponification equivalent for this solid wasfound to be 102.

By utilizing 1 mol of acid to 1 mol of glycerol and interruptingpolymerization before gelation occurs, a soluble or linear type polymeris obtained.

Example 9.A3,5-cyclohexadiene trans-dicarlittle above this temperature.

boxylic acid-1,2 was mixed with a molar excess of ethylene glycol andthe mixture placed in a bath heated to 150.5 C. The temperature of thebatch was rapidly raised and the heating was continued for 1% hours atabout 165 C. to a The system was then evacuated to 4 to 6 mm. of mercurypressure and the temperature of the batch maintained at 170 to 175 C.for 20 minutes. During the entire preparation a streamer carbon dioxidewas passed through the reaction mixture. The water formed by thereaction distilled during the preparation and a small amount ofcrystalline solid was also collected in the distillate during theheating under vacuum. The product col. This solid was soluble in aqueous5% sodium bicarbonate solution, chloroform, acetone and ethyl acetate.It dissolved in hot ethyl and methyl alcohol but deposited from thecooled solution. It was partly soluble in benzene, very slightly solublein boiling water, insoluble in cold water, and insoluble in petroleumether and diethyl ether. A sample of the ester was dissolved inchloroform and the color removed with decolorizing carbon. The polymericester was then precipitated from the filtered chloroform solution by theaddition of petroleum ether and re-precipitated from chloroform withpetroleum ether four times. This purified product was dried in a vacuumdesiccator for 4 days and powdered to yield a white solid. When heatedon a copper block melting point apparatus the polymer started to melt at45 C. The detail data on the properties are as follows:

Per cent carbon 56.67

Per cent hydrogen 5.66 Molecular weight (boiling point method) 810Saponiiication equivalent 95.4 Neutralization equivalent 400 Specificextinction (at 254 m 21.3

The extinction (Brode, Chemical Spectoscopy, 1939) above indicatedrepresents a maximum in fled to,a yellow, glassy solid upon cooling. Theyield was 90.3% of theoretical for a reaction product of equivalentquantities of acid and glycol. The solid polymer possessed solubilitycharacteristics like those of the polymer in Example 9 and it waspurified by the same procedure to yield a white solid which beganmelting at 67 C. when heated on a copper block. Analyses of this polymerwere as follows:

Per cent carbon 55.36 Per cent hydrogen 5.27 Molecular weight (boilingpoint method) 900 Saponification equivalent 94.5 Neutralizationequivalent 409 Example 11.-A polymeric reaction product ofA2,4-cyclohexadiene dicarboxylic acid-1,2 and a polyhydric alcohol isprepared by reacting this acid with ethylene glycol, utilizing themethod and precautions described in Example 9, above, concerning thecorresponding reaction with the A3,5-cyclohexadiene dicarboxylicacid-1,2. Viscous liquid to solid polymeric esters are obtained. Apolymeric ester likewise is derived from A1,4-cyclohexadienedicarboxylic acid-1,2 by re- I action with ethylene glycol at elevatedtemperam with the principles of this invention by interpolymerizationwith othercopolymerizable organic materials to yield a copolymer ormixed polymer. For example, a copolymerized, mixed polyester is obtainedby intercondensation of a mixture of phthalic anhydride, acyclohexadiene dicarboxylic acid, and ethylene glycol to yield thecharacteristic structure the ultraviolet light absorption curve at 254my and is a characteristic exhibited by the parent acid,A3,5-cyclohexadiene transdicarboxylic acid- 1,2. This shows that theproduct was essentially a polymeric ester of this acid. In thepreparation of this ester care was taken to avoid prolonged heating atelevated temperatures, particularly at temperatures above 170 C. Thetotal period of heating was about 2 hours.

Example 10.--A2,6-cyclohexadiene dicarboxylic acid-1,2 was mixed with a10% molar excess of ethylene glycol and the mixture heated at 162.5 to186 C. for 3 hours and 36 minutes when the distillation of water formedby esteriilcation appeared complete. The mixture was then heated at 165to 175 C. under a vacuum of 5 to 6 mm. of mercury pressure for 1 hour.Carbon dioxide was passed through the reaction mixture throughout theheating and a small amount of white solid was collected in thedistillate. The

.product was a viscous yellow liquid which solidi- Or, maleic anhydridemay be substituted for the phthalic anhydride in the foregoing reactionmixture to yield a polyester composition. The unsaturation of thesecopolymers is less active in that they have a reduced rate of airdrying. The extent of reduction in unsaturation activity depends on thereduction in content of the cyclohexadiene dicarboxylic acid nuclei inthe polymeric ester, or, conversely, on the increase in content of lessactively unsaturated acid residues.

Qther polycarboxylic acids, or anhydrides thereof, may be substitutedfor the maleic or phthalic anhydride to produce copolymers or mixedpolymers. Examples of other polycarboxylic acids are: oxalic, succinic,glutaric, adipic, pimelic, azelic, malic, malomaleic, fumaric, tartaric,citric, alkyl malonic acids, citra-conic, mesa-conic, and ita-conicacids. Likewise, mixed polymeric esters or copolymers may be producedwith cyclohexadiene dicarboxylic acids and maleic anhydride "adductswith other dienes; for ex- 13 ample, mixed polymeric esters ofA3,5-cyclohexadiene dicarboxylic acid and an adduct such- 3UP, it ll t IHi where R1 is a residue of long chain fatty acids such as lauric,stearic, oleic, or the like.

Example 13.--The preparation of a mixed ester or copolymer of theforegoing type is illustrated by the following procedure in which thebatch formula was:

g. A3,5 cyclohexadiene trans dicarboxylic acid-1, 2 5.8 g. maleicanhydride 7.8 cc. ethylene glycol The ingredients were mixed and heatedin an oil bath maintained at 150 C. A slow stream of carbon dioxide wasbubbled in the mixture throughout the reaction period. A homogeneoussolution was obtained and the condensation reaction was interruptedafter 1 hours. The final product was lighter in color than the straightor unmixed cyclohexadiene dicarboxylic acid polyester and it possessed alower viscosity. The product also was less soluble in chloroform but wasquite soluble in ethyl acetate.

A coating composition was prepared by dissolving 0.5 g. of the abovemixed polymer in 1 cc. of ethyl acetate and the solution painted on aclean glass plate. This film was exposed to sunlight at room temperatureunder the conditions utilized in Examples 2 and 3 and the plateinspected at intervals. After}? weeks the film had dried appreciably byfurther polymerization, but the drying rate was lower than that of thefilms in Examples 2 and 3. 50 mg. of benzoyl peroxide did not appear toaccelerate the drying rate of an otherwise duplicate preparation of themixed polymer in ethyl acetate.

Polymeric linear type esters of increased molecular weight are producedby effecting condensation polymerization under extremely high vacuum,as, for example, under from about 10" to 10- mm. of mercury pressure inan apparatus such as described in the Journal of the American ChemicalSociety, 54, 1557 (1932). Such polymers are herein termed linearsuper-polymers," since molecular weights are reached by this processwhich are not obtainable under ordinary condensation polymerizationconditions.

mam

In order to prevent cross-linking by addition polymerization duringmanufacture of the linear condensation polymer when it might otherwiseoccur, a polymerization inhibitor may be utilized. Typical inhibitors ofaddition polymerization are compounds of phenolic type, especiallypolyhydric phenols, such as hydroquinone and tertiary butyl catechol.

Throughout this specification and the claims, the term polymerization"has been used in its generic sense'to include either additionpolymerization or condensation polymerization. Addition polymerizationdesignates polymer formation by an addition type reaction, as where acarbon to carbon double bond opens and adds to another double bond; forexample In this type of reaction, elimination of a compound such aswater is not necessary to effect polymer formation. on the contrary, theterm "condensation polymerization is here used to include thosereactions in which polymer formation is effected by repeated eliminationof a reaction product, usually water or an alcohol, for example- (fi-0Hno-n -OR H20 In accordance with these definitions, additionpolymerization includes those reactions in which oxygen may intervene inor activate polymer formation.

Although the specific illustrations here given utilize the free acid inthe esterification reaction, it is to be understood that otherester-forming derivatives of the cyclohexadiene dicarboxylic acids maybe substituted therefor in processes for preparing either the monomericor polymeric esters. Where the acid is of the anhydride-forming type, itis frequently advantageous to substitute the anhydride for the freeacid. Also, it is possible to use other ester-forming derivatives suchas the acid chloride, the amide, or the imide, with liberation of themore volatile HCl or NH: from an anhydrous reaction medium duringesterification. Suitable precautions should be taken to prevent additionof the HCl or NH; to the ester. Ester interchange may be utilized toprepare the polyhydric alcohol esters, as by reacting ethylene glycol orglycerol with the simple methyl ester of the cyclohexadiene acids anddistilling off methyl alcohol as it is freed by the reaction. Othersuitable variations of the methods herein disclosed will be apparent tothose skilled in the art.

The melting points of typical cyclohexadiene dicarboxylic acids andtheir corresponding anhydrides are as follows:

Melting point of- Acid Anbydride 15 I I6 v The melting points ofsome ofthe above acids of this invention may be converted to metal salts. arenot precise due to complications, such as Treatment with an alkali metalhydroxide contendency to isomerize, decompose or to lose water vertsester or terminal acid groups of the polymer and form anhydrides. I tothe alkali metal salts. These alkali metal salts Suitable procedures forpreparing the various 5 may, in turn. be converted to polyvalent metalcyclohexadiene dicarboxylic acids are disclosed in salts by metathesis,e.. g., by reacting aqueous the literature. The A3,5-cyclohexadienetranscalcium chloride with an aqueous dispersion of dicarboxylicacid-1,2 may be prepared, for exthe sodium salt to form sodium chlorideand the ample, by sodium mercury amalgam or electrocalcium salt. lyticreduction. The A3,5-cyclohexadiene trans- 10 Although this invention hasbeen illustrated dicarboxylic acid-1,2 utilized in the speciiic exwithvarious presently preferred processes and amples herein disclosed wasprepared by electroproducts, numerous alterations utilizing theprinlytic reduction of phthalic acid in sulfuric acid ciples thereofwill occur to those skilled in the solution. Such a method is disclosedin Berichte, art, and it is to be understood that the invention volume39 (III) 1906, pages 2933 to 2942. The A2, 15 is not limited to thespecific examples and may acid may be prepared by heating a concentratedbe otherwise embodied or practiced within the solution of the 113,5 acidin water for 9 hours. scope of the appended claims.

By reason of their valuable properties, the I claim: monomers andpolymers of this invention are 1. A polymeric ester ofA3,5-cyclohexadiene dicapable of use in many fields; for example, the acarboxylic acid-1,2 and glycol. polymeric esters may be utilized incoating com- 2. A polymeric ester consisting essentially of positions,molding compositions, in adhesives for the reaction product of A35cyclohexadiene dithe manufacture of laminated glass or plywoodcarboxylic acid and a polyhydric alcohol having and the like. Thesoluble type polymers may be only hydroxyl groups as reactivesubstituents. used in printing inks, coatings on rubber, paper, a 3. Apolymeric ester consisting essentially of or fabrics, as in theproduction of artificial the reaction product of A35 cyclohexadlenedileather. as a primer coating for metal surfaces carboxyiic acid and aglycol havingonly hydroxyl where a bonding agent is desired. Use as acomgroups as reactive substituents.

ponent ofan oxidizing vehicle in varnishes and PAUL c. comarr, paints isa particularly valuable application of a the air drying type polymers.In molding com- REFERENCES TED psitinsv the Valuable thermwemng W 15 Thefollowing references are of record in the a preferred and predominantfeature. Because m of t t of flexibility and good abrasion resistanceobtainy able with the polymeric esters herein described, UNITED BTATEsPATENTS these materials are also adapted for use in or on Number NameDate floor coverings (linoleum, etc), or in electrical 1. .7 Brook! e1?81 M11731. 1 2 insulation, as well as a binder where resistance1.998.744 Ubben Apr. 23, 1935 to shock loads is important. 2,323,706DAlelio July 8,- 1948 The monomeric esters or low polymers may be 0 2. 2Cliflord 0t -1 Dec- 1945 further polymerized alone or copolymerized with1 DA ly 1 4 other monomers or polymers to yield modified 2,421,878Gerhart June 10, 1947 resinous products with improved characteristics,2.445.553 Beavers July 20, 1948 For example, the so-called alkyds may bemodi- OTHER REFERENCES fled with thecyclohexadiene dicarboxylic acidesters to impart valuable thermosetting or air a meme and chem" 1929'drying properties. Further, the polymeric esters

1. A POLYMERIC ESTER OF $3,5-CYCLOHEXADIENE DICARBOXYLIC ACID-1,2 AND GLYCOL. 